运用METATOOL软件对枯草芽孢杆菌（Bacillus subtillis）TZM1012由葡萄糖生物合成胞苷的代谢途径进行分析，以确定胞苷合成的最佳途径和最大理论产率。结果表明其最大理论产率为0.28，5-磷酸核糖焦磷酸与草酰乙酸是胞苷合成途径的关键节点，发酵中后期低溶氧控制是胞苷合成的重要前提，溶氧控制在5%~10%时胞苷产量可提高15.8%。结论是以途径分析为指导，改变外界环境因子，胞苷的产量可得到显著的提高。

METATOOL soft ware was applied to analyze the cytidine biosynthesis pathway in Bacillus subtillis TZM1012．The results was as follows: PRPP and oxaloacetic acid were found to be the key nodes in cytidine biosynthesis pathway and low dissolved oxygen concentration in the medium-term and last periods of fermentation was an important precondition of cytidine biosynthesis. The highest theoretical yield of cytidine was 0.28 and cytidine yield could increased by 15.8% if the dissolved oxygen concentration in fermentation broth was of 5%~10%. According to the analysis of metabolic pathway of cytidine biosynthesis, the yield of cytidine can be greatly improved by changing the environmental factors.